The transformer schematic from the previous page has been redrawn in the top center diagram and it is now possible to derive the formulas for designing an integrated common mode and differential mode inductor. First, it should be noted that the schematic shown is identical to that used to define a coupled inductor used in multi-phase voltage regulators and as a result a more complete account of the equations can be found in the article referenced above. To design an integrated component one must determine how to measure and calculate the values of 2*LK which represents the differential mode inductance and the value of LM which represents the common mode inductance. This can be done by observing, as shown on the left side of the page, if one measures the open circuit inductance between pins 1 and 4, one is effectively measuring LM+LK. If the equivalent reluctance model is drawn for this open circuit inductance, it is clear that this measurement is equal to R + RC in parallel with R. Similarly, as shown on the right side of the page, one can measure the reverse series inductance between pins 1 and 2 with pins 3 and 4 shorted. This yields a measurement of 2*LK. If the equivalent reluctance model is drawn for this reverse series inductance, it is clear that this measurement is equal to RC + 0.5*R. From the above equations one has all of the information necessary to design the inductance parameters of an integrated common mode differential mode inductor, but no information on when or if the inductor will saturate.